An example of a point-to-multipoint optical network can be the passive optical network. Passive optical networks are defined in standards, by well known organizations, for general application. The network is terminated at a single point, typically located in a telecommunications provider central office (CO), in an optical line terminal (OLT) and at multiple subscriber points, typically at the subscriber's residence, by an optical network unit (ONU).
The OLT and the ONUs have single fiber interfaces which transmit and receive optical signals at different wavelengths. The OLT transmits signals at a wavelength λdown and receives signals from the ONUs at a wavelength λup. The ONU transmits signals at a wavelength λup and receives signals from the OLT at a wavelength λdown. The downstream signal broadcasts to all ONUs on the network; while upstream signals from each subscriber ONU are assigned unique time slots according to a time division multiple access (TDMA) protocol.
To support high-data rates and long distances, between the OLT and ONUs, Passive Optical Networks (PONs) use single-mode optical fiber. A key component in any PON is a single-mode optical splitter. The function of a 1×N optical splitter is to split and direct identical copies of the downstream optical signal to each of the each of the N ONU-facing ports.
The same splitter combines N upstream signals into a single, single-mode optical port facing the OLT. The law of energy conservation requires that the downstream signal at each output port will be attenuated by at least a factor of 1/N relative to the input signal. If one assumes that all signals in the upstream are treated identically by the splitter, (i.e. the splitter has no polarization, or wavelength preferences) then a signal entering any one of the N ONU-facing ports must be attenuated by at least a factor of 1/N by the time it reaches the single OLT-facing port, as a consequence of the second law of thermodynamics (entropy cannot decrease in a closed system).
For the ideal single-mode splitter, one that has zero excess loss, the total downstream optical power launched into the splitter is equal to the total power emitted from the N ONU-facing ports. For the same ideal splitter, the total optical power flowing out of the single OLT-facing upstream port can be no more than 1/N times the total optical power launched into any set the N ports. A very large fraction, (N−1)/N of the upstream signal is radiated out of the single mode waveguides in the splitter as dispersed and unusable light energy, which will be called waste-light.
Thus, a need still remains for an optical network communication system with optical line terminal transceiver that compensates for the attenuation of the upstream signal path. In view of the growth in the optical network communication industry, world-wide, it is increasingly critical that answers be found to these problems. In view of the ever-increasing commercial competitive pressures, along with growing consumer expectations and the diminishing opportunities for meaningful product differentiation in the marketplace, it is critical that answers be found for these problems. Additionally, the need to reduce costs, improve efficiencies and performance, and meet competitive pressures adds an even greater urgency to the critical necessity for finding answers to these problems.
Solutions to these problems have been long sought but prior developments have not taught or suggested any solutions and, thus, solutions to these problems have long eluded those skilled in the art.